Thanks for the replies, chaps. I think I might pursue this, as suggested, a bit later down the line. One question - I tried a dodgy blurred profile picture which got rejected but of course noticed that if you pay, you don't need one. Has a lack of a picture ever been a problem for you guys that have succeeded?
Not sharing a clear photo at any point before meeting is not going to automatically mean you don't get anywhere but it will greatly reduce your chances, certainly if you're seeking an 'ordinary' girl rather than an escort type who probably won't care. Guys generally expect to see a picture of a girl, and girls are no different.
Having some sort of public photo rather than just a blank will increase your chances of getting interest. I just have a photo of my torso in suit and tie, with head cropped off - any one will do as long the size is moreorless right.
I then have a couple of very clear face photos in private SA mode which I share with girls I'm interested in, even if we've not been chatting. However, that's a personal choice, obviously. As has been said, some guys prefer to wait till you've been chatting for a bit and are on WhatsApp but that reduces your chances, IMO.
As I'm middleaged and fairly ugly, most girls just ignore me on SA when they see my photo but I calculate that that's better than wasting time messaging and then she saying she's not interested when she finally does see me. One could argue that rejection is less likely if you've chatted a bit and built up a rapport but I believe putting a clear photo early on helps my chances of securing interest, plus I'd like to think I come across well in first message anyway.